The Kingdom of Zegleus has decided to send an envoy to prepare for the threat of invasion from other continents and form a grand alliance. Mitsuha has been assigned to accompany the envoy as the “Lightning Archpriestess.” She is excited about her first trip abroad in the other world, so she prepares an Earth-made camper to ensure a comfortable journey, so soon after the departure from the Kingdom, she, Princess Sabine, and Collette climb aboard and leave the envoy behind. Thus begins the carefree journey of three runaway girls in another world!